The present invention relates to a view adjustment device of a vehicle which adjusts a view recognized by a driver by indicating visual stimulation.
Conventionally, a windshield glass for a vehicle which assists a drive sense (driving feeling) of a driver by providing specified marks at right-and-left both ends of the windshield glass and guiding driver's eyes (gazing point) so that the driver's eyes can be focused on a position located below an imaginary straight line which connects the right and left marks is known (Japanese Patent Laid-Open Publication No. 2008-222204). According to the windshield glass for the vehicle, since it is prevented that the driver's eyes are diffusely directed to a position located above the imaginary straight line, the driver can pay stable attention onto a road.
A technology that a forward view of the driver is so adjusted by shielding a lower end portion of the windshield glass that the driving safety can be improved is known as well. In a view adjusting device of a vehicle disclosed in Japanese Patent Laid-Open Publication No. 2005-75188, there is provided a triangular area at the windshield glass, which has an apex and two sides (right-and-left ridgelines), wherein the apex is located between a driver's facing point and a vehicle's central point which is offset from the driver's facing point, and the two sides (right-and-left ridgelines) extend, slanting uniformly, from the apex toward both ends, in the vehicle width direction, of the base. Herein, the triangular area has a lower visible light transmittance than an outside area of this triangular area (that is, the triangular area has a translucent or non-transparent state of the windshield glass in which driver's forward visibility through the windshield glass is limited), so that parting lines which correspond to the above-described two sides of the triangular area (right-and-left ridgelines) are created by a difference in contrast. Thereby, in addition to the shielding effect of the lower end portion of the windshield glass, fluctuations of a head's inclination angle during vehicle cornering can be suppressed, so that a driving position of the driver is stabilized and thereby disturbance of steering can be suppressed.
The inventors of the present invention recognized a phenomenon that drivers unconsciously direct their eyes toward an outward side in the vehicle width direction when a vehicle travels straightly, in particular, at the time of a high speed traveling. There is a concern that this phenomenon may cause the driver to have an illusion that the vehicle does not have a good straight-traveling stability even if the vehicle is traveling straight properly stably. Herein, the inventors conducted a verification experiment to verify causing factors of this phenomenon. A precondition of the verification experiment will be described first. As shown in FIGS. 8 and 9, a vehicle Va is configured such that a steering wheel 41 is arranged on the right and a direction of an extension line Ea which connects a center 42p of a driver's seat 42, a top 43p of a meter hood 43, and a top 41p of the steering wheel 41 matches a direction of a vehicle-body center line Fa extending in a vehicle longitudinal direction which is a physical front direction of a vehicle body. In FIG. 9, reference characters 44, 45 and 46 denote respective contours of projection images of a windshield glass, a bonnet (engine hood), and a meter hood which are respectively projected on a road surface around a diver's head. Herein, a direction of driver's eyes, that is—a head's rotational angle of the driver, when the vehicle travels straightly at different speeds was measured.
Results of the verification are shown in FIG. 10. As shown in FIG. 10, when the vehicle Va stops, the head's rotational angle is 0 (degree), and the direction of the driver's eyes is the same as the direction of the vehicle-body center line Fa (the direction of the extension line Ea). The driver's head tends to rotate in a right direction when the vehicle traveling speed becomes higher, and the head's rotational angle relative to the vehicle-body center line Fa was 2.4 (degrees) when the vehicle traveling speed was 100 (km/h).
The driver generally perceives and recognizes objects through visual information processing of visual information (optical flow) of the objects obtained through the windshield glass by using the visual function of the driver's both eyes. The eyes' visual function is classified into the function of recognizing different objects with the both eyes concurrently, the function of recognizing objects three-dimensionally (three-dimensional viewing), and the function of recognizing a single object by combining each visual image on the retina of each eye and forming a single image (fusion).
As shown in FIG. 11A, in a case in which the direction of the vehicle-body center line Fa matches the direction of the extension line Ea, the driver theoretically operates the steering wheel 41 so that a target T of the vehicle traveling direction can be positioned on the extension line Ea at the time of the vehicle straight traveling. Therefore, the driver drives the vehicle such that the top 43p of the meter hood 43 and the target T which are positioned on the extension line Ea as marks of vehicle driving overlap each other in front.
As shown in FIG. 11B, in a case in which the steering wheel 41 of the vehicle Va is arranged on the right, a right-side front pillar 47 is provided near a right-side eye Er, so that the right-side eye Er gets a pressure feeling (stress). Further, the visual information which the right-side eye Er can visually recognize through the windshield glass is blocked by the right-side front pillar 47 suddenly, so that this information becomes less than the visual information which a left-side eye El can visually recognize through the windshield glass. Therefore, the left-side eye El which gets less pressing feeling and obtains more visual information becomes a dominant eye tentatively and thereby the predominance of the right-side eye Er decreases relatively. Consequently, since the rate of the fusion of the left-side eye Er becomes higher than that of the right-side eye Er (i.e., becomes predominant), it is assumed that the driver may visually recognize views such that the top 43p of the meter hood 43 is positioned on the right side of the target T by an optical illusion based on the visual information processing. It can be considered that a head's rotation tendency which is caused by the optical illusion based on the visual information processing increases more as the amount of visual information obtained through the windshield glass becomes larger, i.e., the vehicle traveling speed becomes higher.
As shown in FIG. 11C, when the rate of the fusion of the left-side eye El is higher than that of the right-side eye Er, it can be considered that the diver can be theoretically made to visually recognize views such that the top 53b of the meter hood 53 and the target T overlap each other in front by slightly shifting the top 53p of the meter hood 53 to the left (toward the inward side in the vehicle width direction), thereby suppressing the head's rotation of the driver.
Accordingly, as shown in FIGS. 12 and 13, the driver can be made to visually recognize views such that the top 53c of the meter hood 53 and the target T overlap each other in front by shifting the top 53p of the meter hood 53 of the vehicle Vb to the left even when the vehicle traveling speed is high, so that the stability of the vehicle straight traveling by the driver at the time of the high vehicle-speed traveling can be ensured. In FIGS. 12 and 13, reference characters 51, 52, Eb, Fa, 54, 55 and 56 denote the steering wheel, the driver's seat, the extension line connecting tops 51p, 52p, 53p, the vehicle-body center line, the contour of the projection image of the windshield glass, the contour of the projection image of the bonnet, and the contour of the projection image of the meter hood, respectively.
However, while the stability of the vehicle straight traveling at the time of the high vehicle-speed traveling can be ensured in a case in which the position of the top 53p of the meter hood 53 is slightly shifted to the left, the direction of the vehicle-body center line Fa does not match the direction of the extension line Eb, i.e., these two lines do not cross each other, at the time of vehicle stop, in other words. Therefore, there is a concern that the driver may have a sense of discomfort.